Evaluation of a novel osmotically volumetric urine index as a rapid and inexpensive marker for certain renal conditions

Abstract

An open question remains the assessment of the patient's condition in various kidney diseases using inexpensive laboratory methods. The aim of this study was to evaluate the diagnostic tool, the osmolal-volume index of urine, calculated based on urine density and hourly diuresis. A retrospective study of medical records of 86 intensive care unit patients was carried out (34 – with diabetes insipidus, 30 – with acute renal failure, 22 – with chronic renal failure), as well as a prospective study involving 22 healthy individuals without renal pathology. Urine samples were collected three times over a three-hour period; the index and volume of each fraction were measured and averaged. One-way Analysis of Variance was used to evaluate the influence of study groups on osmotically volumetric urine index; means were separated using Fisher’s Least Significant Difference procedure (p < 0.01). There was a significant difference between study groups regarding the proposed index (p < 0.01), and in healthy individuals it ranged from 8.0 to 12.0. In diabetes insipidus, the proposed index sharply decreased, acquiring values below 1.0. At the initial stage of acute renal failure, its value increased (22.0 ± 5.5), while at the stage of polyuria decreased to 2.0. Chronic renal failure was manifested by the index decrease (4.2±2.1). The osmotically volumetric urine index is a dynamic indicator of the efficiency of excretory and concentration renal function applicable for the field hospitals where necessary lab equipment and reagents are unavailable and history of patient’s water consumption, retention, and loss, is known. In case of impaired renal function, this index can vary significantly from 0.02 to 30. The simplicity of the method, its non-invasiveness, plus as the communicativeness, deserve the introduction of this marker into clinical practice